Recreational vehicles are normally built using a "skeletal chassis" of a motor vehicle purchased from a vehicle manufacturer such as Ford, Chevrolet, or Freightliner. As used in this specification, the phrase "skeletal chassis" designates a structure that includes various mechanical components such as the motor, front and rear axles, control pedals, steering wheel and the like, as well as the chassis frame upon which the mechanical components and other items are mounted. However, a skeletal chassis does not include a subfloor or platform structure. Most commonly, the skeletal chassis includes two substantially parallel elongated members or beams that extend for substantially the length the chassis, and upon which the remainder of the recreational vehicle is mounted.
As used in this specification, the term "shell" generally refers to an enclosed structure which extends over the chassis in order to surround the usable space in a recreational vehicle. The skeletal chassis directly or indirectly supports the shell. The shell encloses both the driver compartment in the front portion of the vehicle where various operating controls for the vehicle are located, and the living area which extends from the front portion to the rear portion of the vehicle.
Concerning recreational vehicle structures which have been used heretofore, U.S. Pat. No. 5,314,205, issued to Glesmann, discloses a typical skeletal chassis. The chassis includes two parallel elongated members that extend for substantially the length of the chassis. The elongated members are referred to as chassis rails. These chassis rails are normally constructed with steel beams having a channel-shaped cross-section. The chassis rails are spaced apart, with the length of the rails being dependent upon the variations in the wheel bases of different recreational vehicle. In the direct-chassis-support construction, the shell of the recreational vehicle is mounted directly on the chassis. The twin rails construction provides a desirable flat, long, and straight surface to mount the floor of a recreational vehicle. However, the twin rails construction may not be sufficiently sturdy to protect against bending and twisting forces encountered when the vehicle is driven on the road with pot holes and other irregular surfaces which are often encountered. Furthermore, the bending and twisting forces transfer from the chassis to the shell, and severe shocks may cause the side walls of the shell to crack and fracture. In addition, the direct-chassis-support construction does not provide sufficient accessible storage space for users. It also provides only a limited amount of holding compartments for various functional tanks or vessels (water, propane, holding). Thus, the direct-chassis-support construction method provides only limited solutions to the problem of positioning the tanks and vessels to achieve a balancing weight distribution and, at the same time, maintain accessibility for easy service.
U.S. Pat. No. 4,746,164, issued to Crean, discloses an indirect-chassis-support recreational vehicle construction where a platform is placed between the skeletal chassis and the floor of the vehicle. The Crean construction improves the stability of the recreational vehicle by providing a flat horizontal surface on which to mount the shell. It also increases storage compartments in the space between the skeletal chassis and the floor of the recreational vehicle. However, the storage compartments are not completely accessible from side to side. The lack of accessibility decreases serviceability and thereby increases service costs. Furthermore, the Crean storage compartments are not modular. Thus, the Crean design provides only limited ways to place storage space modules and functional units to balance the weight of the vehicle.
U.S. Pat. No. 5,501,504, issued to Kunz, discloses an improved indirect-chassis support recreational vehicle construction. The Kunz patent proposes placing a superstructure platform between the skeletal chassis and the floor of the vehicle. However, the Kunz platform uses a twin rails construction which, as noted above, does not provide adequate support to protect against bending and twisting forces. Also, the Kunz twin rails are long solid rails which substantially increase the weight of the recreational vehicle. The substantial added weight decreases the gas mileage of the vehicle and thereby increases its operating costs. The Kunz superstructure platform elevates the floor of the recreational vehicle and thereby increases the amount of storage space for users and holding compartments for functional units. However, the added storage space in the Kunz platform, particularly the space between the two platform rails, are not completely accessible. The lack of accessibility decreases serviceability and thereby increases service costs.